The present invention relates to a machine tool system for machining a large-sized workpiece such as an aircraft part mounted on a workpiece mounting table, by moving a spindle having a tool mounted thereon in the directions along the X-axis, the Y-axis and the Z-axis with respect to the workpiece and, more specifically, to a novel machine tool system such as a machining center, which includes a spindle support structure having a spindle arranged to be movable in the directions along the X-axis, the Y-axis and the Z-axis, and a workpiece mounting table opposed to the spindle support structure, the workpiece mounting table having two pallet mounting surfaces and supporting the pallet mounting surfaces to allow them to be rotationally indexed in a desired position, and which can provide a highly efficient, high-speed and highly precise maching even for a large-sized workpiece and requires only a compact area for installation. The present invention also relates to a method for exchanging pallets in the machine tool system.
In the prior art, a method has been employed in which an airframe of an aircraft is constructed by dividing it into small components to be machined and by joining the components with bolts or rivets. In recent years, however, the trend is toward integrating those parts as far as possible and thereby reducing the number of joins. As a result, the parts to be machined have increased in size and have become complicated in shape, thereby giving rise to the demand for a novel machine tool for machining such parts.
The unique performance requirements for such a machine tool include the provision of a table on which a large-sized workpiece to be machined can be mounted, the provision of a sufficient stroke in feed axes to machine the large workpiece and the possibility of machining a large-sized part having a complicated shape at any portion, and in any kind of shape, by a single setup. Further, such a part must be machined efficiently, at a high speed and with high precision. Also, in view of fact that a desired size of a workpiece to be machined will vary from one machine tool user to another, the machine tool having a size required by each user can be manufactured timely and promptly and installed in the factory.
For purpose of fixedly mounting a large workpiece, the table of the machine tool has to be large, and it is necessary to take into consideration that the movability of the large table in the directions along three orthogonal feed axes, i.e., the X- Y- and Z-axes or in the directions along three rotational feed axes, i.e., the A- B- and C-axes is disadvantageous from the viewpoint of high-speed and highly precise machining. More specifically, unlike normal machine tools, a machine tool for machining a large workpiece requires that the spindle rotating with the tool held thereon is provided with orthogonal feed means and rotational feed means and is thereby movable in the directions along orthogonal feed axes and in the directions along rotational feed axes, in order to allow the workpiece to be machined with the table being fixed (in a stationary state) during the machining.
It is noted that the X-axis and the Y-axis are orthogonal to each other in a vertical plane, and extend horizontally and vertically, respectively, while the Z-axis extends in a horizontal direction perpendicular to the X-axis and the Y-axis. It is also noted that the directions along the A- B- and C-axis are defined as the directions of rotation about the X- Y- and Z-axes, respectively.
In addition, as a large workpiece is liable to deteriorate the efficiency of a workpiece setup process, it is required to provide means for automatically changing the workpiece thereby to improve the efficiency of the setup process and an operating rate of the machine tool.
Generally, in case that the workpiece is machined to a desired shape by a machine tool such as a machining center, the desired machining of the workpiece is efficiently performed by mounting the workpiece on a pallet and by exchanging the pallets between the pallet stocker and the workpiece mounting table of the machine tool including the table.
For such an efficient pallet exchange, components such as a pallet stocker acting as a setup station for performing the setup process therein, pallet changing means for replacing one pallet having a workpiece mounted thereon with another by transferring and carrying them, a pallet magazine for storing a plurality of pallets having a workpiece mounted thereon and pallet transferring means for transferring the pallets between the pallet magazine and the pallet stocker are required. Therefore, the large-sized machine tool for handling the pallets having relatively large workpiece mounted thereon is uselessly enlarged in its entire installation area unless these components are provided.
Further, such large workpieces are often mounted on the pallets by a vacuum method and may fall off the pallets, if the pallets are transported in a vertical state, to harm the workers in the worst case. In addition, the pallets in the vertical state are poorly balanced during the transportation, and some the workpieces mounted on the pallets may decline the pallets thereby to make it seriously difficult to mount the pallets on the workpiece mounting table of the machine tool. It is, therefore, desirable that the pallets having the large workpiece mounted thereon are handled in the horizontal state.
Further, in case that the large workpiece is machined, the time required for a setup process of mounting a workpiece on a pallet and for an exchange process of pallets is often substantially equal to that required for activating the machine tool to actually machine the workpiece. Therefore, since the setup time and the pallet exchanging time occupy a considerable ratio to that required for machining one workpiece, the shortening of the setup time and the pallet changing time may directly achieve high-speed machining and an improved machine operating rate.
A first prior art available for realizing the aforementioned requirements is a symmetric multiaxial linear motor machine tool, as disclosed in Unexamined Japanese Patent Publication (Kokai) No. 8-318445. The machine tool includes a vertical gantry movable in a direction along the X-axis on vertically opposed frames, a saddle movable in a direction along the Y-axis on the vertical gantry, a ram adapted to be movable in a direction along the Z-axis on the saddle, a spindle head disposed at the front end portion of the ram for rotatably supporting a spindle having a tool mounted thereon, and a table fixed on the front portion of the frame for mounting a workpiece thereon. The machine tool is driven to move in the individual feed directions along the X- Y- and Z-axes by linear motors. Moreover, the vertical gantry is guided on two sides, upper and lower sides, with respect to the frame and is driven by the linear motors. A stator (static element) and a mover (moving element) of the linear motor are arranged on the frame in vertically symmetric manner so that the attraction force of the stator acting on the mover both in the upper and lower linear motors may be vertically offset from each other.
A second prior art available for realizing the aforementioned requirements is a machine tool as disclosed in Unexamined Japanese Patent Publication (Kokai) No. 9-262727. The machine tool includes a vertical bed in the shape of a rectangular frame having a through opening at its center, as viewed in front view, an X-slide in the shape of a rectangular frame shape made movable on the front side of the vertical bed in a direction along the X-axis and having a through opening at its center, as viewed in front view, a Y-slide adapted to be movable in a direction along the Y-axis while being supported and guided in the through opening of the X-axis slide, a Z-axis slide adapted to be movable in a direction along the Z-axis while being supported and guided by the Y-axis slide, a spindle head disposed at the front end portion of the Z-axis slide for rotatably supporting a spindle having a tool mounted thereon, and a table fixed on the front portion of the vertical bed for mounting a workpiece thereon. The machine tool is guided in the feed directions along the X- Y- and Z-axes individually by a pair of rail-shaped guides and is driven by a pair of linear motors.
Further, a third available prior art is a workpiece pallet exchange method, as disclosed in Unexamined Japanese Patent Publication (Kokai) No. 60-29261. The machine tool with a pallet changer, as disclosed therein, includes a machine body for machining a workpiece by relative movement along the X- Y- and Z-axes between a spindle head for rotatably supporting a spindle having a tool mounted thereon and a table for mounting the workpiece thereon, and a pallet changer disposed adjacent to the machine body for giving and receiving the pallets to/from the table to exchange them. The pallet changer has a plurality of surfaces for mounting pallets thereon and is constructed to rotate about a horizontal rotational axis and thereby to index a pallet change position, a standby position or a workpiece cleaning position.
Further, a fourth available prior art is a pallet changer, as disclosed in Unexamined Japanese Patent Publication (Kokai) No. 10-128640. This shuttle type pallet changer, after the desired machining has been finished, carries a pallet having a machined workpiece mounted thereon from the table of a machine tool to a pallet stocker, and then carries a pallet having a new setup workpiece mounted thereon from the pallet stocker to the table of the machine tool. At the mounting/demounting of the workpiece on/from the pallet, an angle plate mounted on the pallet is turned by 90 degrees to a horizontal state, and the machined workpiece is removed by a crane or the like. After this, the new setup workpiece is mounted on the angle plate.
Further, a fifth available prior art is an aerial carrying apparatus, as disclosed in Unexamined Japanese Utility Model Publication (Kokai) No. 60-120751. This carrying apparatus includes a moving device movable in a longitudinal direction of carrying rails disposed over a machine tool, in a vertical direction and in direction perpendicular to the former directions, and a holding device suspended from the moving device for holding a pallet having a workpiece mounted thereon. The pallet held by the holding device is carried to a predetermined position in the machine tool.
Further, a sixth available prior art is an automatic machining apparatus, as disclosed in Unexamined Japanese Utility Model Publication (Kokai) No. 4-57358. This automatic machining apparatus is provided with a carriage and a hoist crane for carrying a workpiece between a three-dimensional storage disposed in front of a machine tool and a carrying-in table serving as a setup station as well as between the three-dimensional storage and a workpiece changer. If the carriage breaks down, the workpiece is carried by the hoist crane between the three-dimensional storage and the carrying-in table serving as the setup station and between the three-dimensional storage and the workpiece changer of the machine tool.
In a large-sized machine tool for machining large parts such as a machine tool for machining aircraft parts, a workpiece mounting table for a large workpiece to be mounted is generally stationary during the machining process. Therefore, a spindle, which has a tool mounted thereon and can rotate, is provided with the orthogonal feed means and the rotational feed means thereby to allow for the movement in the directions along the X-axis, the Y-axis and the Z-axis and the rotation along the A-axis, the B-axis and the C-axis. Further, such a machine tool generally has a horizontal-type spindle and also has relatively long strokes along the X-axis and the Y-axis. Therefore, a high large-sized column is guided to move in the horizontal direction along the X-axis on a bed so that a spindle head rotatably supporting the spindle can be moved in the direction along the Y-axis on the column.
As one of methods for solving the above-described problem that the mover of the spindle support structure is large and heavy, it is possible that a base is designed to have a frame-shaped structure and to be provided with X-axis guides at two portions, upper and lower portions of the base, as in the first and second prior arts, so that a X-axis slider similarly designed to have a frame-shaped structure can be guided to move along the upper and lower guides. With such a guiding and driving at the two upper and lower portions, the mover is not cantilevered. Therefore, the rigidity required for the mover can be lowered thereby to ensure the necessary rigidity even in a lighter mover. If the linear motors are used as means for feeding/driving the mover, a high-speed feed can also be achieved.
However, there arises a new problem which is particular to the machine tool requiring a longer X-axis stroke than that of the typical machine tool. As the X-axis stroke becomes longer, a telescopic type or winding type movable cover for covering the guides and the feed mechanism in the direction along the X-axis has to become longer in order to provide a protection against chips produced by machining the workpiece. As a result, the movable cover can easily break down.
The first and second prior arts do not indicate such a problem because they are not directed to the machine tool having a relatively long X-axis stroke. Further, although the X-axis slider is lightened, the Y-axis stroke is also increased in length to exert certain degree of load on the X-axis guides. This can raise another problem that safety has to be ensured for the lifetime of the X-axis guides.
As a result of the use of the large-sized workpiece, it takes a long time to perform the setup operations, i.e., to mount the workpiece on the table, to remove chips from the workpiece after it is machined, and to remove the workpiece from the table after machined. During the setup operations, therefore, the machine tool is interrupted to raise a problem that the operating rate of the machine drops. Further, the mover (or the spindle head and the columns) to move in the direction along the X-axis has to be increased in size and weight. This can raise problems that the high-speed feed is difficult, and that maintaining the positioning precision in the direction along the X-axis at a high level is difficult due to the frictional resistance caused by the weight of the mover moving in the direction along the X-axis.
One of solutions for solving the problem of the drop in the working efficiency and the operating rate of the machine due to the long time required for the setup is to attach a pallet changer to the machine tool, as exemplified in the third prior art. If a large workpiece is to be handled, however, a large installation space is required and consequently, the construction has to be enlarged. This causes another problem in that the necessary cost is considerably high.
In order to improve the efficiency and safety of the setup operations by carrying out the setup operations with the workpiece mounting surfaces of the pallet being in horizontal state, the fourth prior art can be employed. In the fourth prior art, however, the pallet changer and the pallet stocker are merely arranged in a plane. Therefore, in case that the pallet having the large workpiece mounted thereon is changed, the fourth prior art raises a problem in that the area for installing the machine tool is seriously enlarged.
Further, in the fourth prior art, it is sequentially necessary, after the desired machining, to carry the pallet having the machined workpiece mounted thereon from the table of the machine tool to the pallet stocker by the shuttle type pallet changer, to move the table of the machine tool to a position facing another pallet stocker and to carry the pallet having the new setup workpiece mounted thereon from the pallet stocker to the table of the machine tool by the pallet. Therefore, the fourth prior art has another problem in that it takes a long time to exchange the pallets.
According to the fourth prior art, unless the pallet having the machined workpiece mounted thereon is carried out of the table of the machine tool, the pallet having the new setup workpiece mounted thereon cannot be carried to the table of the machine tool. During this process, therefore, the machining process in the machine tool has to be stopped. As a result, this can raise a problem that the whole time necessary for one machining process is longer.
Further, in the fourth prior art, the pallet having the workpiece mounted thereon is carried in the plane after a desired machining process. Therefore, the operation of checking the machined workpiece by the operator is accompanied with a serious danger, and the access to the workpiece is deteriorated. This results in problems of a decreased operating efficiency in the checking and cleaning operations for the machined workpiece and impossible direct setup operation.
From these problems, it is deal for saving the space required for the machine tool to carry the pallet not in a plane but in a three-dimensional space.
By utilizing the fifth prior art, therefore, the pallet is not carried in the plane, as in the fourth prior art, but can be carried in the space above the machine tool. In this case, however, the positioning of the pallet held in the holding device suspended from the moving device is problematic. This is because an object suspended from a moving device may rock during the movement, thereby to make it seriously difficult to position the object at a predetermined position.
Further, in the fifth prior art, the suspended pallet is positioned with respect to the machine tool by the positioning means disposed on the machine tool. Therefore, it is necessary to provide the positioning means on the machine tool, and this results in the increased cost of the machine tool. Even if the pallet is positioned on the machine tool, the pallet stocker or the like also has to be provided with the positioning means thereby to raise a problem that the construction is seriously complicated.
In the sixth prior art, as in the fifth prior art, the pallet is carried in the space above the machine tool, and the hoist crane is especially used for carrying the pallet. The positioning of the suspended pallet is an important target, as described hereinbefore. In the sixth prior art, however, no countermeasure has been provided for positioning the workpiece suspended by the hoist crane. Therefore, a problem is that it is seriously difficult to carry the pallet to the predetermined position and to position it precisely.
From the above discussion, it can be said that it is a requirement not only to carry the pallet spatially for saving the space of the machine tool but also to position the pallet suspended and held simply and reliably at the predetermined position and to achieve a highly efficient and precise machining.
An object of the present invention is to solve the above-described problems and to provide a machine tool system, and a method for exchanging pallets therein, which allow for the high-speed and precise machining a large-sized workpiece and which facilitate the setup process for the large-sized workpiece.
Another object of the present invention is to provide a machine tool system, and a method for exchanging pallets therein, for machining a large-sized workpiece in a high operating rate of the machine.
Another object of the present invention is to provide a machine tool system, and a method for exchanging pallets therein, which can make an installation area compact.
Another object of the present invention is to provide a machine tool system, and a method for exchanging pallets therein, which allow for a highly efficient machining by reducing the time for exchanging the workpieces.
Another object of the present invention is to provide a machine tool system, and a method for exchanging pallets therein, which can improve the access to the workpiece and allow for a direct setup operation.
Another object of the present invention is to provide a machine tool system, and a method for exchanging pallets therein, which can perform the operation of checking the machined workpiece safely and easily even during the machining of the workpiece.
Another object of the present invention is to provide a machine tool system, and a method for exchanging pallets therein, for a large-sized workpiece, which can handle chips easily.
In view of the aforementioned objects, the present invention provides a machine tool which includes a spindle support structure having a spindle movable in directions along the X-axis, the Y-axis and the Z-axis, and a workpiece mounting table disposed in opposed relation to the spindle support structure and having two opposed pallet mounting surfaces, which workpiece mounting table is supported to allow the pallet mounting surface to be rotationally indexed in a desired position. This machine tool can machine the workpiece with a pallet being positioned on a pallet a vertical state, after mounting the pallet on one pallet mounting face of the workpiece mounting table in a horizontal state.
According to the present invention, there is provided a machine tool for machining a workpiece mounted on a workpiece mounting table by moving a spindle having a tool mounted thereon in directions along the X-axis, the Y-axis and the Z-axis with respect to the workpiece, which includes a spindle support structure including a spindle head rotatably supporting the spindle and arranged to be movable in the directions along the X-axis, the Y-axis and the Z-axis on a base adapted to be located on a floor surface; a workpiece support structure disposed in opposed relation to said spindle support structure and including a workpiece mounting table having two opposed pallet mounting surfaces and pallet securing means arranged thereon, the workpiece mounting table supported to allow for rotational indexing about a horizontal axis extending in the direction along the X-axis; and rotationally indexing means for turning the workpiece mounting table of the workpiece support structure by 90 degrees or 180 degrees to allow the two opposed pallet mounting surfaces to be positioned in an upwardly directed horizontal position or a transversely directed vertical position.
The rotationally indexing means may be constructed to comprise an indexing motor for rotationally indexing the workpiece mounting table of the workpiece support structure, first positioning means for positioning the workpiece mounting table by engaging with the rotating shaft of the workpiece mounting table of the workpiece support structure, a bracket mounted on the workpiece mounting table of said workpiece support structure, and second positioning means for positioning the workpiece mounting table of the workpiece support structure by engaging with the bracket.
The spindle support structure may be constructed to comprise a base adapted to be located on the floor surface and having guides extending in the direction along X-axis on the upper and lower portions thereof, an X-axis slider guided along the guides on the upper and lower portions of the base to move from side to side in the direction along the X-axis, a Y-axis slider guided on the X-axis slider to move upwardly and downwardly in the direction along the Y-axis, a Z-axis slider guided on the Y-axis slider to move forwardly and backwardly in the direction along the Z-axis, and a spindle head fixedly mounted on the Z-axis slider or mounted to be rotatable in at least one of directions along the A-axis, the B-axis and the C-axis.
The base of the spindle support structure may be configured of an extended base having a plurality of base units coupled to each other along the X-axis, the base unit having a predetermined X-axis unit length, and the workpiece support structure may be configured of an extended workpiece support structure having a plurality of workpiece support structure units coupled to each other along the X-axis with the horizontal axes thereof aligned with each other, the workpiece support structure unit having a predetermined X-axis unit length.
The X-axis slider of the spindle support structure may be driven in the direction along the X-axis by linear motors disposed along the guides on the upper and lower portions of the base, respectively, and the liner motor may include a stator and a mover arranged on the base and the X-axis slider, respectively, in opposed relation to each other so that the attraction force of the stator acting on the mover reduces the load in the gravitational direction exerted on the guides of the X-axis slider.
The base of the spindle support structure may have longitudinal spaces extending in the direction along the X-axis and opening downwardly in the upper and lower portions of the base, respectively, and each of longitudinal spaces accommodates therein a guide for guiding and supporting the X-axis slider and X-axis feed means for moving the X-axis slider in the direction along the X-axis.
According to the present invention, there is also provided a machine tool for machining a workpiece mounted on a workpiece mounting table by moving a spindle having a tool mounted thereon in directions along the X-axis, the Y-axis and the Z-axis, which includes a spindle support structure including a spindle head rotatably supporting the spindle and arranged to be movable in the directions along the X-axis, the Y-axis and the Z-axis on a base adapted to be located on a floor surface; a workpiece support structure disposed in opposed relation to the spindle support structure and including a workpiece mounting table having two opposed pallet mounting surfaces and pallet securing means arranged thereon, the workpiece mounting table supported to allow for rotational indexing about a horizontal axis extending in the direction along X-axis; rotationally indexing means for turning the workpiece mounting table of the workpiece support structure by 90 degrees or 180 degrees to allow the two opposed pallet mounting surfaces individually to be positioned in an upwardly directed horizontal position and a transversely directed vertical position; and chip discharge means interposed between the spindle support structure and the workpiece support structure for discharging chips produced in the machining area to the outside of the machining area.
According to the present invention, there is also provided a machine tool for machining a workpiece mounted on a workpiece mounting table by moving a spindle having a tool mounted thereon in directions along the X-axis, the Y-axis and the Z-axis with respect to the workpiece, which includes a spindle support structure including a spindle head rotatably supporting the spindle and arranged to be movable in the directions along the X-axis, the Y-axis and the Z-axis on a base adapted to be located on a floor surface; a workpiece support structure disposed in opposed relation to the spindle support structure and including a workpiece mounting table having two opposed pallet mounting surfaces and pallet securing means arranged thereon, the workpiece mounting table supported to allow for rotational indexing about a horizontal axis extending in the direction along the X-axis; a pallet stocker spaced apart from the workpiece support structure for a pallet having the workpiece mounted thereon to be placed; and pallet changing means for transferring and carrying the pallet between the pallet mounting surface of the workpiece mounting table of the workpiece support structure in an upwardly directed horizontal position and the top surface of the pallet stocker, by holding the pallet in a suspended manner and by moving along guiding means in the horizontal direction and in the vertical direction.
According to the present invention, there is also provided a machine tool for machining a workpiece mounted on a workpiece mounting table by moving a spindle having a tool mounted thereon in directions along the X-axis, the Y-axis and the Z-axis with respect to the workpiece, which includes a spindle support structure including a spindle head rotatably supporting the spindle and arranged to be movable in the directions along the X-axis, the Y-axis and the Z-axis on a base adapted to be located on a floor surface; a workpiece support structure disposed in opposed relation to the spindle support structure and including a workpiece mounting table having two opposed pallet mounting surfaces and pallet securing means arranged thereon, the workpiece mounting table supported to allow for rotational indexing about a horizontal axis extending in the direction along the X-axis; a pallet stocker spaced apart from the workpiece support structure for a pallet having the workpiece mounted thereon to be placed; pallet changing means for transferring and carrying the pallet between the pallet mounting surface of the workpiece mounting table of the workpiece support structure in an upwardly directed horizontal position, and the top surface of the pallet stocker, by holding the pallet in a suspended manner and by moving along guiding means in the horizontal direction and in the vertical direction; a three-dimensional pallet magazine spaced apart from the pallet stocker and configured to be able to store a plurality of pallets in a three-dimensional manner; and pallet transferring means interposed between the pallet stocker and the three-dimensional pallet magazine and arranged to be movable in the horizontal direction and in the vertical direction for transferring the pallets between the pallet stocker and the three-dimensional pallet magazine.
According to the present invention, there is also provided a machine tool for machining a workpiece mounted on a workpiece mounting table by moving a spindle having a tool mounted thereon in directions along the X-axis, the Y-axis and the Z-axis with respect to the workpiece, which includes a plurality of spindle support structures including a spindle head rotatably supporting the spindle and arranged to be movable in the directions along the X-axis, the Y-axis and the Z-axis on a base adapted to be located on a floor surface; a plurality of workpiece support structures disposed individually in opposed relation to the plurality of spindle support structures, each of the workpiece support structures including a workpiece mounting table having two opposed pallet mounting surfaces and pallet securing means arranged thereon, the workpiece mounting table supported to allow for rotational indexing about a horizontal axis extending in the direction along the X-axis; a plurality of pallet stockers individually spaced apart from the plurality of workpiece support structures for a pallet carrying having the workpiece mounted thereon to be placed; a plurality of pallet changing means for transferring and carrying the pallet between the pallet mounting surface of the workpiece mounting tables of the workpiece support structures in an upwardly directed horizontal position and the top surface of the pallet stockers individually spaced apart from the plurality of workpiece support structures, by holding the pallet in a suspended manner and by moving along guiding means in the horizontal direction and in the vertical direction; a three-dimensional pallet magazine spaced apart from the plurality of pallet stockers and configured to be able to store a plurality of the pallets in a three-dimensional manner; and pallet transferring means interposed between the plurality of pallet stockers and the three-dimensional pallet magazine and arranged to be movable in the horizontal direction and in the vertical direction for transferring the pallets between the plurality of pallet stockers and the three-dimensional pallet magazine.
According to the present invention, there is also provided a machine tool for machining a workpiece mounted on a workpiece mounting table by moving a spindle having a tool mounted thereon in directions along the X-axis, the Y-axis and the Z-axis with respect to the workpiece, which includes a spindle support structure including a spindle head rotatably supporting the spindle and arranged to be movable in the directions along the X-axis, the Y-axis and the Z-axis on a base adapted to be located on a floor surface; a workpiece support structure spaced away from the spindle support structure and including a workpiece mounting table having one pallet mounting surface and pallet securing means arranged thereon, the workpiece mounting table supported to allow for rotational indexing about a horizontal axis extending in the direction along the X-axis; rotationally indexing means by turning the workpiece mounting table of the workpiece support structure by 90 degrees or 180 degrees to allow the one pallet mounting surface to be positioned in an upwardly directed horizontal position and a transversely directed vertical position; and chip discharge means interposed between the spindle support structure and the workpiece support structure for discharging chips produced in the machining area, to the outside of the machining area.
According to the present invention, there is also provided a machine tool for machining a workpiece mounted on a workpiece mounting table by moving a spindle having a tool mounted thereon in directions along the X-axis, the Y-axis and the Z-axis with respect to the workpiece, which includes a spindle support structure including a spindle head rotatably supporting the spindle and arranged to be movable in the directions along the X-axis, the Y-axis and the Z-axis on a base adapted to be located on a floor surface; a workpiece support structure spaced apart from the spindle support structure including a workpiece mounting table having one pallet mounting surface and pallet securing means arranged thereon, the workpiece mounting table supported to allow for rotational indexing about a horizontal axis extending in the direction along the X-axis; a pallet stocker spaced apart from the workpiece support structure for a pallet having the workpiece mounted thereon to be placed; and pallet changing means for transferring and carrying the pallet between the pallet mounting surface of the workpiece mounting table of the workpiece support structure in an upwardly directed horizontal position and the top surface of the pallet stocker, by holding the pallet in a suspended manner and by moving along guiding means in the horizontal direction and in the vertical direction.
According to the present invention, there is further provided a pallet carrying system of a machine tool for transferring and carrying a pallet having a workpiece mounted thereon between a workpiece mounting table and a pallet stocker in the machine tool, which includes the workpiece mounting table of the machine tool having two pallet mounting surfaces and supported to allow for rotational indexing; a pallet stocker spaced apart from the workpiece mounting table for a pallet to be placed; and pallet changing means for transferring and carrying the pallet between the pallet mounting surface of the workpiece mounting table in an upwardly directed horizontal position and the upper surface of the pallet stocker, by holding the pallet in a suspended manner and by moving along guiding means in the horizontal direction and in the vertical direction.
According to the present invention, there is also provided a pallet carrying system of a machine tool for transferring and carrying a pallet having a workpiece mounted thereon between a workpiece mounting table and a pallet stocker in the machine tool, which includes the workpiece mounting table of the machine tool having two pallet mounting surfaces and supported to allow for rotational indexing; a pallet stocker spaced apart from the workpiece mounting table for a pallet to be placed; pallet changing means for transferring and carrying the pallet between the pallet mounting surface of the workpiece mounting table in an upwardly directed horizontal position and the top surface of the pallet stocker, by holding the pallet in a suspended manner and by moving along guiding means in the horizontal direction and in the vertical direction; a three-dimensional pallet magazine spaced apart from the pallet stocker and configured to be able to store a plurality of pallets in a three-dimensional manner; and pallet transferring means interposed between the pallet stocker and the three-dimensional pallet magazine and arranged to be movable in the horizontal direction and in the vertical direction for transferring the pallets between the pallet stocker and the three-dimensional pallet magazine.
According to the present invention, there is further provided a method of exchanging pallets in a machine tool including a spindle support structure having a spindle movable in directions along the X-axis, the Y-axis and the Z-axis with respect to the workpiece, and a workpiece mounting table which is disposed in opposed relation to the spindle support structure and which has two pallet mounting surfaces and is supported to allow the pallet mounting surfaces to be rotationally indexed in a desired position, which includes steps of (a) mounting a pallet having a workpiece mounted thereon on one pallet mounting surface of the workpiece mounting table being in a horizontal state; (b) machining the workpiece with the pallet being positioned in a vertical state; (c) after the workpiece is machined, mounting another pallet having another workpiece mounted thereon on the other pallet mounting surface of the workpiece mounting table being in the horizontal state, after the workpiece is machined; (d) demounting the pallet having the machined workpiece mounted thereon from the workpiece mounting table with the pallet being in the horizontal state; and (e) machining the another workpiece with the another pallet having the another workpiece mounted thereon being positioned in the vertical state.
With such constructions as described above, in the spindle support structure, the X-axis slider, i.e., one of the components of the mover movable with respect to the stationary base, is guided and supported by the upper and lower edge portions, so that forces (i.e., a thrust force and a supporting force) acting on the X-axis slider are applied to substantially symmetric portions of the X-axis slider. Unlike the case of the cantilever support in the machine tool of the prior art, therefore, the X-axis slider is not required to be reinforced by the structural member in order to prevent the bending and deflection of a distal end portion, as caused by the rotation moment, so that the structure can be lightened and moved at a high speed. In the machine tool, especially a machine tool for machining an large-sized workpiece, the stroke along the X-axis is generally elongated. Therefore, making the mover at a higher speed in the X-axis direction significantly contributes to an increased machining speed for the whole machine tool and a reduced operating time thereby to improve an efficiency in the maching process.
Moreover, provision of the workpiece mounting table supported to allow for rotational indexing about the horizontal axis extending in the direction along the X-axis allows the workpiece mounting surface to be directed upwardly or preferably horizontally. As a result, the risk of the workpiece falling down from the workpiece mounting surface can be eliminated and the safety of the worker can be ensured. This facilitates the setup process.
Moreover, one of the two opposed pallet mounting surfaces of the workpiece mounting surface can be positioned in the horizontal state or in the vertical state by the rotational indexing means. Therefore, the machined workpiece can be set up and transferred/carried while a new workpiece is being machined, thereby to improve the operating rate of the machine and to shorten the time required for exchanging the workpieces to achieve a highly efficient machining process.
Further, the pallet having the workpiece mounted thereon is carried over the operator or worker. This can make the area for installing the machine compact and improve the access of the worker to the workpiece thereby to make a direct setup operation possible.
Moreover, the chip discharge means is intended to lighten the chip removing operation by discharging chips and cutting fluid, which are produced in the machining area and fall naturally, to a predetermined place. The chip discharge means can separate the spindle support structure from the workpiece support structure to facilitate the manufacture and installation of the large-sized machine tool so that the spindle support structure and the workpiece support structure can be modularized.
By combining the effects achieved by the constructions described above, the machine tool and the method of exchanging pallets according to the present invention can reduce the time required for the setup process and the machining process thereby to improve the efficiency of the whole machining operation.
Comparing the aforementioned prior arts to the present invention, the first and second prior arts disclose the machine tool having a relatively short X-axis stroke, unlike the machine tool according to the present invention having a relatively long X-axis stroke for maching the large-sized work workpiece, and therefore, fails to solve any of the problems such as the malfunction of the movable cover and the lifetime of the X-axis guide. In the third and fourth prior arts, the pallet changer and the pallet stocker are merely arranged in the plane, while the machine tool apparatus according to the present invention conveys the pallet in the air so that it is free from the problem of the larger area for installing the machine. In the fifth prior art the positioning of the pallet carried in the air with respect to the machine is carried out by the machine, and in the sixth prior art, the pallet is merely carried in a suspended manner by the hoist crane. On the other hand, the machine tool according to the present invention is provided on the pallet changer with means for positioning the pallet with respect to the machine so that the structure of the machine can be simplified without the least modification of the machine tool.